Pegvisomant is a synthetic drug that binds to cell receptors where GH would normally bind, thus preventing the naturally occurring hormone from stimulating IGF-1 and bone growth as it normally would. This study will see if pegvisomant will reduce blood levels of IGF-1 and mitigate the effects of growth hormone excess, including bone pain, bone turnover, hand and foot swelling and sweating, and abnormal levels of related hormones.